Pros: The most museum-quality phone design yet from Apple, packing the most powerful iPhone hardware in history into the smallest and sleekest enclosure. Overall camera performance is outstanding, even by comparison with low-end dedicated still and video cameras, with configuration-free video calling an option over Wi-Fi. New 960x640 display equals past iPhones in brightness and off-angle viewability while surpassing them by a factor of four in detail, improving the smoothness of photos and fonts. Improved speaker performance across the board, and markedly better microphone performance in handset mode amidst ambient noise. Markedly faster data performance under some conditions. Reasonably priced given the technology inside.

Two features in the iPhone 4 are most notably improved from the iPhone 3GS, and the screen is one of them. Apple refers to it as a “Retina Display” because the 960x640 resolution on a 3.5” diagonal screen translates to 326 pixels per inch, smaller than the human eye can individually perceive. In short, the iPhone 4 screen is capable of rendering graphics that are equivalent in sharpness to the output from some color laser printers—assuming they were printing on a 3-inch by 2-inch surface. Combined with the 800:1 contrast ratio, four times the prior iPhone’s, the screen enables photographs and artwork to feature smoother curved lines and gentler color variations than on any past iPhone or iPod touch.

Comparisons with the iPhone 3GS screen reveal that iPhone 4’s display is slightly yellow tinted—a “warm” color balance relative to the pink-tinted 3GS—with roughly identical brightness at their respective lowest, middle, and highest levels. Tests of identical applications running on the two screens repeatedly and conclusively showed the iPhone 4 screen to be superior: old 480x320 artwork is rendered with crisper lines, while updated applications with higher-resolution art and text just look nicer on the newer display—smoother and more realistic, with only the faintest hint that dots are being used to create the images. DVD-quality videos that previously played on the iPhone, iPhone 3G, and 3GS at downscaled resolution are presented in their full glory on the iPhone 4 screen, and the device now plays HD 720p videos, slightly downscaled, but still with more detail than the best-looking standard-definition films. Apple’s processors also enable iPhone 4 to display 3-D games with the same Open GL 2.0 special effects found on iPhone 3GS, but with dramatically improved textures and curvier lines.

But in fairness, iPhone 4’s screen deserves both praise for its technical excellence and criticism on the software side. Apple has done little to make better use of the new screen from a user interface standpoint, replacing fonts and control graphics with smoother versions, but includes almost nothing else to show off iPhone 4’s capabilities. Moreover, the screen has become data-hungrier at a time when new iPhone customers are being required to purchase limited data plans, calling into question the wisdom of relying on a cellular network to feed the phone map, video, or other visual content. Fully loading maps on iPhone 4 actually takes longer than on the iPhone 3G and 3GS because more data is being gathered to fill the high-resolution screen, even though the actual benefit to the user—imperceptibly small details in a tiny space—is modest. Loading a 9.7” iPad screen with all that data makes sense, but cramming it all into the little iPhone 4 will burn through a low-capacity data plan unnecessarily.

Cellular Calling and Data Performance. Though we discuss the performance of iPhone 4’s Phone application in far greater detail in the next section of this review, we’ll note that voice calling performance of this iPhone is at least as strong as on iPhone 3GS, subject to a couple of caveats. First, gaps and heavy user demands on AT&T’s network have been the primary causes of dropped calls on past iPhones, and given the surge of new customers who are already buying iPhone 4s, AT&T will need to radically improve its network to handle calls more reliably in some areas. In our primary testing area in Western New York, however, prior iPhone models very rarely dropped calls, and iPhone 4 hasn’t had any problems of that sort at all. That having been said, there are ways that iPhone 4 can be held unnaturally for calling purposes that can impact its antenna performance, which as discussed subsequently can be eliminated by using a case.

On paper, the only change Apple has made to iPhone 4’s 3G data performance is support for HSUPA, a high-speed data upload protocol with up to 5.76 Megabit per second transfer speeds, which augments the theoretical maximum 7.2 Megabit per second download speeds of HSDPA, previously supported by Apple—and, importantly, some international carriers—in the iPhone 3GS. Most U.S. cities have lacked for HSDPA- and HSUPA-enabled cellular towers, which led iPhone 3GS users to see performance well under those theoretical maximums in this country, but the Canadian cellular network operated by Rogers was more advanced, so iPhone 3GS hardware in Toronto routinely outperformed the units we tested in multiple U.S. cities. AT&T has continued to make selective enhancements to its data network on a city-by-city, neighborhood-by-neighborhood basis, and the iPhone 4 is ready for such improvements—capable of doing even better than the iPhone 3GS, particularly when sending e-mails and other data, at least under the right conditions.

Under supposedly 4-5-bar AT&T signal conditions, our iPhone 4s achieved peak download speeds of nearly 3.1 Megabits per second (note: updated from prior 1.9 Megabit per second result after further testing in different neighborhoods), with most results in the 1.6 Megabit per second range—an improvement over iPhone 3GS speeds that fell between 0.5 Megabits per second to 1.2 Megabits per second in the U.S., but not over Canadian speeds in the 3-4.5Mb/second range. Upload speeds ranged from 0.9 to 1.2 Megabits per second, a huge improvement over iPhone 3GS speeds in the 0.25 range in both the U.S. and Canada. However, there are significant variations in the speeds iPhone 4 actually achieves in different areas resulting from AT&T tower and congestion differences, as well as drops in speed due to Apple antenna engineering issues. Depending on where we were testing, holding the iPhone 4 normally in the hand either had no effect on transfer rates, or literally stopped speed tests from running at all over a cellular connection—a nearly complete loss of data service when iPhone 4’s steel antenna band was touched in certain ways. Your performance will vary based on where you live and work, whether you’re inside or outside, and what sort of physical contact you’re making with the iPhone 4’s antenna band during use. Using rubber and plastic cases completely eliminated this issue in our testing. We expect that Apple and AT&T will be addressing some of these performance irregularities in the near future. You can see a video of the reception issue in action here.

802.11n. Unlike all three earlier iPhones, iPhone 4 includes support for 802.11n, the most recent Wi-Fi standard to reach mass consumer adoption—and one that is found in most wireless routers shipping today. Though Apple caveats this new feature by noting that iPhone 4 only supports 2.4GHz 802.11n, a limitation that prevents the device from joining 5GHz 802.11n networks, it will work on dedicated 2.4GHz 802.11n networks, and mixed 802.11b/g/n networks, including the ones created by Apple’s recent dual-band routers. Even on a mixed network, the result is a very tangible download speed improvement: 9-10 Megabits per second on iPhone 4 versus 5-7 Megabits per second on iPhone 3G or 3GS, with nearly identical upload speeds in the 0.9-1.1 Megabit per second range. Results will vary based on your broadband connection, and on the web sites you visit, but if you’re using an 802.11n 2.4GHz mixed network, expect web pages and other Internet-dependent data streamers to load roughly 50% faster than on a 3GS when you’re on Wi-Fi, with little change when you’re sending e-mails.

Transfer Speeds and Storage Capacities. Test transfers between two iTunes 9.2-equipped Macintosh computers took an average of 1 minute and 20 seconds to move 1GB of audio and video content to the iPhone 4, roughly on par with prior versions, assuming that other data transfers weren’t taking place on the USB ports at the same time. Slower speeds were observed when other devices were active on the USB chain, as would be expected.

It’s worth noting that, like past iPods and iPhones, the storage capacities on Apple’s boxes aren’t precisely reflective of the actual available space on the 16GB and 32GB iPhone 4s. The 16GB iPhone 4 starts with 13.8GB of usable storage space, and the 32GB starts with 28.8GB of space, partially due to the footprint of the iOS 4 operating system. We found use of the 16GB model to be extremely cramped between apps, media files, and the products of iPhone 4’s still and video cameras, such that we would be disinclined to recommend the 16GB model to users who expect to take frequent advantage of the photo, HD video, and app features. Adding a single GPS application to iPhone 4 will consume 1.5GB or more, and HD movies are each routinely 3GB in size. From our perspective, Apple’s 32GB iPhone 4 is a smarter purchase for such people; the 16GB model will suffice for less demanding users.

Battery Performance.

Due to a combination of a larger battery and more efficient processors than in prior iPhone models, iPhone 4’s battery life is touted as superior—and our tests confirmed this.

- Wi-Fi Web Browsing: Apple promises 10 hours of battery life. The same exact test from above using Wi-Fi on a mixed 802.11b/g/n network ran for 8 hours and 35 minutes. Superior performance would be expected if the 3G antenna was turned off, but disabling or limiting iPhone 4’s calling features during web browsing isn’t in our view a real-world test of its performance.

- Audio Playback. Apple promises 40 hours of battery life. Our test of this feature has not yet concluded, but based on the current status of our testing, we believe that the iPhone 4 will easily exceed Apple’s claim. Even without disabling 3G or Wi-Fi, our test iPhone 4 at 50% volume with headphones is using 20% of its battery life every 10 hours and 20-some minutes, which is to say that a 51-hour run time appears likely at this time. Updated: The iPhone 4 audio test result came in at 52 hours and 45 minutes, handily exceeding Apple’s promised run time—even without the device’s wireless radio hardware turned off to conserve power.

- 3G Talk Time: Apple promises 7 hours of battery life. Our test of an iPhone 4 with 3G and Wi-Fi both on ran for 7 hours and 6 minutes of continuous 3G talk time, doing nothing else in the foreground, while an iPhone 4 with Wi-Fi off ran for 7 hours and 22 minutes of continuous 3G talk time.

- FaceTime: Apple makes no assurances as to the run time for this feature. In our tests, FaceTime ran over Wi-Fi continuously for 3 hours and 10 minutes. Two separate iPhone 4 units showed battery loss of 30% per hour on mixed 802.11b/g/n networks.

- 720p Video Recording: Apple makes no assurances as to the run time for this feature. Our 720p video recording session ran continuously for 3 hours and 3 minutes, though recording had to be restarted every 50 minutes as the camera is not designed to create video files longer than that.

As a general rule, iPhone 4 will require less mid-day charging as a multipurpose device than the iPhone 3G and 3GS—a very welcome though not ideal return to the calling battery life of the original iPhone, with considerably more power under the hood in this newer model. While further battery improvements are still needed, the option to stretch iPhone 4’s life by switching to EDGE for calling purposes does exist, expanding the promised calling time to 12 hours. We don’t recommend actually doing this due to its negative impact on iPhone 4’s numerous data features, but it’s an option.

Click Below to Read the Rest of This Review:

Editors' Note: iLounge only reviews products in "final" form, but many companies now change their offerings - sometimes several times - after our reviews have been published.
This iLounge article provides more information on this practice, known as revving.